Serological analysis of Melan-A(MART-1), a melanocyte-specific protein homogeneously expressed in human melanomas

Immunohistochemical expression of melan-A and tyrosinase in uveal melanoma

Background

Melan-A and tyrosinase are new immunohistochemical markers that can be used in the diagnosis of melanocytic lesions. The aim of this study was to investigate the correlation between radiotherapy or clinicohistopathological parameters and the expression of melan-A and tyrosinase in uveal melanoma.

Methods

Thirty-six enucleated cases of uveal melanoma were studied. The formalin-fixed, paraffin-embedded specimens were immunostained with monoclonal antibodies against melan-A and tyrosinase. The samples were classified as either positive or negative. The chi-square or the Student-t tests were used to test for the correlation of the expression rates of melan-A and tyrosinase with clinico-pathological parameters.

Results

Melan-A and tyrosinase were positive in 33 (91.7%) and 35 (97.2%) of the specimens, respectively. There was no significant association between the expression of melan-A or tyrosinase and radiotherapy or any clinico-pathological parameter. All specimens were positive for at least one of the immunohistochemical markers.

Conclusion

To the best of our knowledge this is the first study concluding that the expression of melanocytic markers such as melan-A and tyrosinase is not influenced by radiotherapy or any clinico-pathological parameter. Moreover, when tyrosinase and melan-A are used together, 100% of the formalin-fixed, paraffin-embedded uveal melanoma samples tested positive for one of those markers.

Small cell carcinoma of the submandibular gland: a rare small round blue cell tumor

The presence of small cell carcinoma within the submandibular gland is an uncommon clinical entity. However, other small round blue cell tumors are encountered in the head and neck with greater frequency. These include lymphoma, Ewing's sarcoma, melanoma, esthesioneuroblastoma, and neuroblastoma. A basic knowledge of the immunohistochemical studies available to distinguish each these tumors from one another significantly improves the frequency of accurate and timely initial diagnosis. We report a case of small cell carcinoma of the submandibular gland and review the other common small round blue cell tumors that occur within the head and neck. We utilize an acronym, LEMONS, to organize our review and facilitate improved retention of the differential diagnosis for small round blue cell tumors of the head and neck.

Non-malignant migration of B16 mouse melanoma cells in the neural crest and invasive growth in the eye cup of the chick embryo

Melanocytes originate from the neural crest. In a previous study, we observed that human SK-Mel 28 human melanoma cells resumed neural crest cell migration after transplantation into the chick embryo neural tube. Here, we used transgenic mouse B16-F1 melanoma cells transfected with green fluorescent protein-vasodilator-stimulated phosphoprotein construct to extend these observations. After the injection of a cell suspension into the trunk neural tube of E2 chick embryos, the migration of melanoma cells was followed by live fluorescence microscopy. Within 12 h, the melanoma cells formed clusters in the neural tube at the levels of the intersegmental clefts between somites. After 24 h, a segmental pattern of emigration was visible. Emigrated melanoma cells were identified in serial paraffin sections by immunohistochemistry with ab732 as a marker for melanoma cells and by in-situ hybridization of mouse-specific repetitive genomic sequence mL1. After 24 h, melanoma cells were found along the medial neural crest pathway and in the sympathetic trunk ganglia and, after 48 h, also in the lateral melanocytic pathway. During migration along the neural crest pathways, mouse melanoma cells underwent apoptosis, which was assessed by anti-caspase 3 and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick-end labeling staining. To prove the ablation of malignant behavior after back-transplantation into the original embryonic neural crest environment, we injected the same cell suspension into the eye cup of the E3 embryo. In this location, invasive melanomas formed.

Melan-A/MART-1-Specific CD4 T Cells in Melanoma Patients: Identification of New Epitopes and Ex Vivo Visualization of Specific T Cells by MHC Class II Tetramers

Over the past decade, many efforts have been made to identify MHC class II-restricted epitopes from different tumor-associated Ags. Melan-A/MART-1(26-35) parental or Melan-A/MART-1(26-35(A27L)) analog epitopes have been widely used in melanoma immunotherapy to induce and boost CTL responses, but only one Th epitope is currently known (Melan-A51-73, DRB1*0401 restricted). In this study, we describe two novel Melan-A/MART-1-derived sequences recognized by CD4 T cells from melanoma patients. These epitopes can be mimicked by peptides Melan-A27-40 presented by HLA-DRB1*0101 and HLA-DRB1*0102 and Melan-A25-36 presented by HLA-DQB1*0602 and HLA-DRB1*0301. CD4 T cell clones specific for these epitopes recognize Melan-A/MART-1+ tumor cells and Melan-A/MART-1-transduced EBV-B cells and recognition is reduced by inhibitors of the MHC class II presentation pathway. This suggests that the epitopes are naturally processed and presented by EBV-B cells and melanoma cells. Moreover, Melan-A-specific Abs could be detected in the serum of patients with measurable CD4 T cell responses specific for Melan-A/MART-1. Interestingly, even the short Melan-A/MART-1(26-35(A27L)) peptide was recognized by CD4 T cells from HLA-DQ6+ and HLA-DR3+ melanoma patients. Using Melan-A/MART-1(25-36)/DQ6 tetramers, we could detect Ag-specific CD4 T cells directly ex vivo in circulating lymphocytes of a melanoma patient. Together, these results provide the basis for monitoring of naturally occurring and vaccine-induced Melan-A/MART-1-specific CD4 T cell responses, allowing precise and ex vivo characterization of responding T cells.

Desmoplastic melanoma: comparison of expression of differentiation antigens and cancer testis antigens

Desmoplastic melanoma is a diagnostic and therapeutic challenge. Immunohistochemical analysis with antibodies to melanoma antigens can complement morphologic evaluation. Although staining for S100 protein is generally positive, staining for other melanoma differentiation antigens, particularly gp100, Melan-A/MART1 and tyrosinase, is often negative despite being commonly positive in other melanoma types. A high clinical index of suspicion and better diagnostic techniques are essential as atypical features and incorrect diagnosis can lead to poor clinical outcomes. Antigens associated with melanoma, such as the melanocyte differentiation and cancer testis antigen, may become important targets for immune therapies. We characterized the patterns of antigen expression of desmoplastic melanoma from 32 patients, including gp100, Melan-A/MART-1, tyrosinase, MAGE-A1, MAGE-A4 and NY-ESO-1. Consistent positive staining with S100 was observed. Differentiation antigens were expressed more frequently than cancer testis antigens regardless of the histological subtype of desmoplastic melanoma. When present, cancer testis antigen expression correlated to positive staining with differentiation antigens. The diagnostic yield of desmoplastic melanoma did not increase with the addition of cancer testis antigen typing. Low levels of expression of cancer testis antigen may indicate that they are suboptimal targets for vaccine development in desmoplastic melanoma.

New generation vaccine induces effective melanoma-specific CD8+ T cells in the circulation but not in the tumor site

Although increasing evidence suggests that CTL are important to fight the development of some cancers, the frequency of detectable tumor-specific T cells is low in cancer patients, and these cells have generally poor functional capacities, compared with virus-specific CD8(+) T cells. The generation with a vaccine of potent CTL responses against tumor Ags therefore remains a major challenge. In the present study, ex vivo analyses of Melan-A-specific CD8(+) T cells following vaccination with Melan-A peptide and CpG oligodeoxynucleotides revealed the successful induction in the circulation of effective melanoma-specific T cells, i.e., with phenotypic and functional characteristics similar to those of CTL specific for immunodominant viral Ags. Nonetheless, the eventual impact on tumor development in vaccinated melanoma donors remained limited. The comprehensive study of vaccinated patient metastasis shows that vaccine-driven tumor-infiltrating lymphocytes, although activated, still differed in functional capacities compared with blood counterparts. This coincided with a significant increase of FoxP3(+) regulatory T cell activity within the tumor. The consistent induction of effective tumor-specific CD8(+) T cells in the circulation with a vaccine represents a major achievement; however, clinical benefit may not be achieved unless the tumor environment can be altered to enable CD8(+) T cell efficacy.

Concordant loss of melanoma differentiation antigens in synchronous and asynchronous melanoma metastases: implications for immunotherapy

Because of its known heterogeneity, the analysis of antigen expression is crucial prior to the initiation of antigen-specific immunotherapy for melanoma. The melanoma differentiation antigens gp100, MART-1 and tyrosinase are involved in a common pathway of melanin synthesis. Peptides derived from these melanoma differentiation antigens are used in the immunotherapy of melanoma and antibodies recognizing these antigens are commonly applied to detect melanocytic lesions. One hundred and ninety-one paraffin-embedded melanoma metastases from 28 patients with 2-19 lesions (mean, 6.8) developing synchronously (n = 67) or asynchronously (n = 124) were analysed by immunohistochemistry for the expression of the melanoma differentiation antigens, as well as cancer/testis antigens of the melanoma antigen-A (MAGE-A) family (monoclonal antibodies 77B and 57B), anti-S100 and SM5-1. The overall reactivities were 81.6% (gp100), 79.5% (MART-1), 59.6% (tyrosinase), 59.1% (77B), 60.7% (57B), 93.2% (S100) and 91.6% (SM5-1). Twenty-seven lesions (14.1%) were positive for all tumour-associated antigens, 75 lesions (39.2%) were negative for one antigen and 87 lesions (45.5%) were negative for several tumour-associated antigens. Co-ordinated loss was found for lesions negative for gp100 and MART-1 (9.4%, P < 0.0005), gp100 and tyrosinase (11.0%, P = 0.009), MART-1 and tyrosinase (15.2%, P < 0.0005) and gp100, MART-1 and tyrosinase (8.9%, P < 0.0005), which is up to six times higher than the expected calculated loss. This co-ordinated loss of melanoma differentiation antigens in melanoma did not include cancer testis antigens and S100 or SM5-1. On average, the melanoma differentiation antigens stained 50-65% of cells within a lesion, and 10-39% of synchronous clusters were heterogeneous for melanoma differentiation antigen expression. In conclusion, broader polypeptide vaccines should be used for melanoma immunotherapy.

A Novel Approach to Characterize Clonality and Differentiation of Human Melanoma-Specific T Cell Responses: Spontaneous Priming and Efficient Boosting by Vaccination

Despite major progress in T lymphocyte analysis in melanoma patients, TCR repertoire selection and kinetics in response to tumor Ags remain largely unexplored. In this study, using a novel ex vivo molecular-based approach at the single-cell level, we identified a single, naturally primed T cell clone that dominated the human CD8(+) T cell response to the Melan-A/MART-1 Ag. The dominant clone expressed a high-avidity TCR to cognate tumor Ag, efficiently killed tumor cells, and prevailed in the differentiated effector-memory T lymphocyte compartment. TCR sequencing also revealed that this particular clone arose at least 1 year before vaccination, displayed long-term persistence, and efficient homing to metastases. Remarkably, during concomitant vaccination over 3.5 years, the frequency of the pre-existing clone progressively increased, reaching up to 2.5% of the circulating CD8 pool while its effector functions were enhanced. In parallel, the disease stabilized, but subsequently progressed with loss of Melan-A expression by melanoma cells. Collectively, combined ex vivo analysis of T cell differentiation and clonality revealed for the first time a strong expansion of a tumor Ag-specific human T cell clone, comparable to protective virus-specific T cells. The observed successful boosting by peptide vaccination support further development of immunotherapy by including strategies to overcome immune escape.

Identification of two Melan-A CD4+ T cell epitopes presented by frequently expressed MHC class II alleles

Because of its expression pattern restricted to cells of the melanocytic lineage and to melanoma cells, Melan-A is an important target of immunotherapeutic approaches for the treatment of melanoma. Identification of Melan-A derived sequences recognized by specific T cells is therefore of great interest for the development of these therapeutic strategies. Using circulating CD4(+) T cells from healthy donors, we identified two Melan-A-derived CD4(+) T cell epitopes mapping to the 1-20 and 91-110 regions of the protein and restricted by HLA-DR11 and HLA-DR52 molecules, respectively. CD4(+) T cells specific for the identified epitopes were able to recognize the native antigen when endogenously expressed by antigen presenting cells and tumor cells. In addition, CD4(+) T cells specific for Melan-A 91-110 recognized the epitope after exogenous processing and presentation of Melan-A recombinant protein. Identification of these epitopes will be instrumental for the evaluation of the immune response to Melan-A in cancer patients.

Tumor antigen expression in melanoma varies according to antigen and stage

PURPOSE

Melanoma cells express antigens that can induce T-cell and antibody responses. Obtaining a detailed understanding of antigen expression in primary and metastatic melanoma is essential if these molecules are to be useful targets for immunotherapy of melanoma.

EXPERIMENTAL DESIGN

Malignant melanomas (n = 586) from 426 patients were typed for antigen expression. Multiple samples were available from 86 individuals, enabling analysis of antigen expression patterns over time. Paraffin-embedded samples were tested by immunohistochemistry for the presence of the differentiation antigens: gp100, Melan-A, tyrosinase, and the "cancer/testis" antigens MAGE-A1, MAGE-A4, and NY-ESO-1.

RESULTS

Samples were primary tumors (n = 251), lymph node metastases (n = 174), s.c. metastases (n = 71), and distant metastases (n = 90). The differentiation antigens were strongly expressed in 93% to 95% of tumors regardless of stage. In contrast, the frequency of cancer/testis antigen expression in primary tumors for MAGE-A1, MAGE-A4, and NY-ESO-1 was lower (20%, 9%, and 45%, respectively). MAGE-A1 and MAGE-A4 were acquired with advancing disease (to 51% and 44% in distant metastases, respectively) but not NY-ESO-1, which remained positive in 45%. MAGE-A1 expression was twice as prevalent in ulcerated primaries as in nonulcerated primaries (30% versus 15%; P = 0.006) and in thicker as opposed to thin melanomas (26% versus 10%; P = 0.1).

CONCLUSIONS

This large series describes patterns of antigen expression in melanoma and their evolution over time. This will help inform decisions about selection of patients and target antigens for melanoma immunotherapy clinical trials.

Ultraviolet A exposure might increase metastasis of mouse melanoma: a pilot study

BACKGROUND

The major sources of long-wave ultraviolet A radiation (UVA; 320-400 nm) exposure are extensive sunbathing and tanning in solaria. While the carcinogenic effects of mid-wave ultraviolet B radiation (UVB; 280-320 nm) are well recognized, the potentially hazardous effects of UVA are less understood. Several studies have shown that a variety of physiological processes in the cell are modified by UVA exposure, some of which might be involved in the regulation of tumor metastasis. In this study we suggest that UVA radiation could lead to the increase of metastatic capability of melanoma cells in mice.

METHOD/RESULT

A pilot in vivo study was executed using C57BL/6 mice and syngeneic B16 melanoma cell lines. Mice were intravenously (i.v.) injected with either B16-F1 or B16-F10 melanoma cells into the tail vein and then immediately exposed to UVA. Fourteen days after melanoma injection, lungs were collected and the quantity and quality of metastases were determined under a dissecting microscope. As an outcome of the pilot study we observed that i.v. injected melanoma cells formed more lung metastases in the UVA-exposed mice in comparison with the control mice.

CONCLUSION

This result suggests that the UVA exposure of mice, with melanoma cells present in blood circulation, increases the formation of melanoma metastases in lungs. Further studies should determine whether a similar pro-metastatic effect, as observed in mice, could occur in humans and whether other than melanoma tumors might be susceptible.

HMB-45 may be a more sensitive maker than S-100 or Melan-A for immunohistochemical diagnosis of primary oral and nasal mucosal melanomas

BACKGROUND

Primary mucosal melanomas (MMs) of the head and neck are a rare entity. Melanomas with characteristic melanin-pigmented tumor cells are easy to diagnose, but those without melanin-pigmented tumor cells, amelanotic melanomas, are difficult to identify and need immunohistochemistry (IHC) to confirm the final diagnosis. In this study, we examined the expression of three melanocytic differentiation markers, HMB-45, S-100, and Melan-A in primary oral and nasal MMs. We tried to evaluate whether HMB-45, S-100, and Melan-A were useful for diagnosis of primary oral and nasal MMs and to find out which marker was the best of the three.

METHODS

This study used IHC to examine the expression of HMB-45, S-100, and Melan-A in 17 formalin-fixed paraffin-embedded specimens of primary oral and nasal MMs. The staining intensities (SIs) and labeling indices (LIs) of HMB-45, S-100, and Melan-A in 17 MMs were calculated and compared between any two markers.

RESULTS

Immunostaining results showed that the positive rate was 94% (16 of 17) for HMB-45, 88% (15 of 17) for S-100, and 71% (12 of 17) for Melan-A in 17 MMs. The SI of HMB-45 was significantly higher than that of S-100 (P = 0.0011) or of Melan-A (P = 0.0034). In addition, the mean LI of Melan-A (59 +/- 43%) was significantly lower than that of HMB-45 (83 +/- 28%, P = 0.0065) or of S-100 (79 +/- 33%, P = 0.0237).

CONCLUSIONS

Our results indicate that both HMB-45 and S-100 show a high positive rate and LI in MMs and therefore may be good markers for immunohistochemical diagnosis of primary oral and nasal MMs. In addition, HMB-45 may be a more sensitive marker than S-100 because HMB-45 shows a significantly higher SI than S-100 in this study.

CD34 expression in primary cutaneous malignant melanoma: apropos of a case and review of the aberrant melanoma phenotype

BACKGROUND

The histological diagnosis of malignant melanoma can be challenging. Immunohistochemical techniques may define a critical role in certain cases, specifically in establishing a primary diagnosis of melanoma. CD34 is a hemopoietic stem cell antigen expressed in bone marrow and endothelial cells, and may also be expressed in vascular and spindle cell tumors; it is generally negative in malignant melanoma.

CASE REPORT

An 83-year-old white female presented with a 3-4 mm area on her right upper back, which had been present for several years. Histologic sections showed a polypoid distortion by sheets and nodules of transformed amelanotic melanocytes lying in intimate apposition to an attenuated epidermis without a concomitant radial growth phase. Tumor cells were extensively S-100 and CD34 positive and showed focal immunoreactivity with melan-A and HMB-45.

DISCUSSIONS

We present a case of malignant melanoma of nodular subtype, which strongly expressed CD34. The spectrum of abnormal phenotypes in malignant melanoma is reviewed, and a possible explanation for the presence of CD34 is discussed. This case demonstrates the potential of malignant melanoma to express CD34, defining an infrequently recognized aberrant phenotype. Whether or not expression of this marker is associated with a more aggressive clinical course remains to be determined.

Intratumoral T-cell infiltrates and MHC class I expression in patients with stage IV melanoma

The infiltration of tumors by T cells has been shown to correlate with prolonged patients' survival. However, it remains unclear why only some tumors are infiltrated with T cells. This study was designed to investigate possible correlations between intratumoral T-cell infiltrates and the expression of cancer-associated antigens and MHC class I and II molecules in patients with melanoma. Fresh frozen samples from 124 stage IV melanoma patients were analyzed by immunohistochemistry for the expression of Melan-A/MART-1, tyrosinase, gp100, NY-ESO-1, and MHC class I and II. Intratumoral T-cell and B-cell infiltrates were detected by staining with anti-CD4, anti-CD8, anti-CD3, and L26 antibodies. The NY-ESO-1 serum antibody status was assessed by Western blot analysis. Intratumoral CD8+ and CD4+ T cells were detected in 63.9% and 71.3% of patients, respectively. We observed a significant heterogeneity of the expression of the melanocyte differentiation antigens, NY-ESO-1, and MHC class I and II molecules. The only significant correlation was found between the expression of MHC class I and the presence of CD4+ and CD8+ T cells (P < 0.0001). There was a strong association between these two variables with respect to the density and distribution of infiltrating T cells and the pattern of MHC class I expression (focal versus homogenous). Intratumoral T-cell infiltration is closely correlated with the MHC class I expression but not with the expression of differentiation antigens, cancer-associated antigens, or MHC class II molecules. These results may have implications for the definition of prognostic variables and for the identification of patients who may benefit from antigen-specific cancer immunotherapy.

Large cell calcifying Sertoli cell tumor of the testis: Comparative immunohistochemical study with Leydig cell tumor

Large cell calcifying Sertoli cell tumor is a rare type of testicular tumor. Reported herein is a Japanese patient with this tumor not associated with Carney's complex. An 11-year-old boy was admitted to hospital because of left testicular enlargement, and radical orchiectomy was performed. Macroscopically, the tumor was well circumscribed and had a maximum diameter of approximately 2 cm. The cut surface showed a yellow-white solid mass. Histologically, the tumor was composed of large neoplastic cells with abundant eosinophilic cytoplasm with a tubular, trabecular, and solid arrangement and loose myxoid stroma with irregularly shaped calcification. Immunohistochemically, the tumor cells were positive for vimentin, S-100 protein, calretinin, inhibin-alpha, melan-A, and CD10, and type IV collagen and laminin were observed in the extracellular matrix around the tumor cells. The distributions of melan-A, CD10, and mitochondria were characteristically patchy; in contrast, they were diffusely distributed in the cytoplasm in a control case of Leydig cell tumor. The differences in immunostaining patterns for melan-A, CD10, and mitochondria as well as positivity for S-100 protein-beta might be useful diagnostic hallmarks of large cell calcifying Sertoli cell tumor for discrimination from Leydig cell tumor.

Immunohistochemical Analysis of Novel Monoclonal Antibody PNL2 and Comparison With Other Melanocyte Differentiation Markers

PNL2 is a novel monoclonal antibody, which has recently been introduced as an immunohistochemical reagent to stain melanocyte and tumors derived thereof. In the present study, we analyzed the immunoreactivity of this mAb in various normal tissues, melanocytic nevi, primary and metastatic melanoma, nonmelanocytic tumors, including histologic mimickers of melanoma as well as angiomyolipoma, and multiple cell lines derived from different tumors types. We used several tissue microarray panels as well as selected conventional sections from tissue blocks. For metastatic melanoma, immunoreactivity for PNL2 was compared with A103 (Melan-A/MART-1), T311 (tyrosinase), HMB45 (gp100), and D5 (MITF). Positive staining with PNL2 was found in normal melanocytes and neutrophils, but no other normal cell type. Among melanocytic lesions, both benign nevi as well as primary malignant melanomas, especially epithelioid variants thereof, were commonly immunopositive. Only 1 of 13 desmoplastic melanomas reacted with PNL2. PNL2 showed high sensitivity for metastatic melanoma (87%). In comparison, 82% of metastatic melanomas were positive for A103, 76% for HMB45, 92% for T311, and 84% for D5. The combined use of all five reagents minimized the number of immunonegative cases. None of the selected nonmelanocytic tumors (carcinomas or soft tissue neoplasms) was positive for PNL2 in this series except for angiomyolipomas and chronic myeloid leukemias and 1 single case of a malignant peripheral nerve sheath tumor with heterologous differentiation (malignant Triton tumor). Despite its reactivity with neutrophils, PNL2 appears to be a valuable supplementary reagent for the diagnosis of melanocytic tumors.

Ubiquitylation of a melanosomal protein by HECT-E3 ligases serves as sorting signal for lysosomal degradation

The production of pigment by melanocytic cells of the skin involves a series of enzymatic reactions that take place in specialized organelles called melanosomes. Melan-A/MART-1 is a melanocytic transmembrane protein with no enzymatic activity that accumulates in vesicles at the trans side of the Golgi and in melanosomes. We show here that, in melanoma cells, Melan-A associates with two homologous to E6-AP C-terminus (HECT)-E3 ubiquitin ligases, NEDD4 and Itch, and is ubiquitylated. Both NEDD4 and Itch participate in the degradation of Melan-A. A mutant Melan-A lacking ubiquitin-acceptor residues displays increased half-life and, in pigmented cells, accumulates in melanosomes. These results suggest that ubiquitylation regulates the lysosomal sorting and degradation of Melan-A/MART-1 from melanosomes in melanocytic cells.

The use and application of special techniques in assessing melanocytic tumours

To improve diagnostic accuracy, a number of novel techniques have been developed to assist in the evaluation of melanocytic tumours. Dematologists have begun to explore the use of new instruments, such as dermoscopy or confocal scanning laser microscopy, in their clinical assessment of pigmented lesions. They have also benefited from advances in digital photography and applied this technique to monitor patients with numerous atypical naevi. Likewise, the diagnostic armamentarium of pathologists has been enriched over the past decade. A number of new reagents have become available for immunohistochemical analysis of melanocytes in archival material, such as antibodies to tyrosinase, Melan-A/Mart-1, micropthalmia-associated transcription factor and PNL2. These markers have allowed improvements in the sensitivity and specificity in the diagnosis of melanoma and its distinction from histological mimics. However, some pitfalls in the use of various reagents have also become apparent. Most recently, molecular techniques are being explored for their potential use in the diagnosis of melanoma. In this review, various modalities are discussed with regard to their application in the evaluation of melanocytic neoplasms.

Differentiation of human melanoma cells induced by cyanidin-3-O-beta-glucopyranoside

Great attention has been recently given to a flavonoid of the anthocyanin class, cyanidin-3-O-beta-glucopyranoside (C-3-G), which is widely spread throughout the plant kingdom, and is present in both fruits and vegetables of human diets. In this study, we investigated the effect of C-3-G on proliferation and differentiation of human melanoma cells. Both morphological and functional parameters were evaluated, using electron and confocal microscopy, cytofluorometric analysis, HPLC assay, Western blot analysis, and enzymatic assay, as appropriate. A treatment with a single dose of C-3-G decreased cell proliferation without affecting cell viability and without inducing apoptosis or necrosis. The mitotic index and cell percentage in S phase were significantly lower in C-3-G treated cells compared with untreated control. C-3-G treatment induced, in a dose- and time-dependent manner, melanoma cell differentiation characterized by a strong increase in dendrite outgrowth accompanied with a remodeling of the microtubular network, a dramatic increase of focal adhesion and an increased expression of "brain specific" cytoskeletal components such as NF-160 and NF-200 neurofilament proteins. C-3-G treatment also induced increase of cAMP levels and up-regulation of tyrosinase expression and activity resulting in an enhanced melanin synthesis and melanosome maturation. Up-regulation of the melanoma differentiation antigen Melan-A/MART-1 in treated cells respect to the untreated control was also recorded. Data obtained provide evidence that a single treatment with C-3-G is able to revert the human melanoma cells from the proliferating to the differentiated state. We conclude that C-3-G is a very promising molecule to include in the strategies for treatment of melanoma; also because of its nutritional relevance.

Melan A (A103) is expressed in adrenocortical neoplasms but not in renal cell and hepatocellular carcinomas

Most adrenocortical neoplasms, renal cell carcinomas, and hepatocellular carcinomas are diagnosed by a combination of clinical and morphologic features. However, occasionally this histologic differential diagnosis requires additional ancillary tests, such as immunohistochemistry. The authors investigated the potential value of A103 in the differential diagnosis of these tumors. Thirty-two adrenocortical neoplasms, 86 renal cell carcinomas, and 57 hepatocellular carcinomas were evaluated by immunohistochemistry using a monoclonal antibody A103 and a standard ABC method. The adrenocortical neoplasms were 21 adenomas and 11 carcinomas. Thirty-one of the 32 adrenocortical neoplasms showed strong and diffuse granular cytoplasmic staining for Melan A. No nuclear reaction was observed. There were no differences in staining patterns between adrenocortical adenomas and carcinomas. With the exception of one clear cell renal cell carcinoma, all non-adrenocortical neoplasms were negative. The authors conclude that A103 is a useful addition to the immunohistochemical panel in the differential diagnosis of adrenocortical neoplasms from both renal cell and hepatocellular carcinomas. This marker, however, does not separate benign from malignant adrenocortical neoplasms.

Identification of an antigenic peptide derived from the cancer-testis antigen NY-ESO-1 binding to a broad range of HLA-DR subtypes

NY-ESO-1 is a SEREX-defined cancer-testis antigen of which several MHC I, but only few MHC II-restricted epitopes have been identified. Searching for highly promiscuous MHC II-restricted peptides that might be suitable as a CD4+ stimulating vaccine for many patients, we used the SYFPEITHI algorithm and identified an NY-ESO-1-derived pentadecamer epitope (p134-148) that induced specific CD4+ T-cell responses restricted to the HLA-DRB1 subtypes *0101, *0301, *0401, and *0701 that have a cumulative prevalence of 40% in the Caucasian population. The DR restriction of the p134-148 pentadecamer was demonstrated by inhibition with an HLA-DR antibody and a functional peptide displacement titration assay with the pan-DR-binding T-helper epitope PADRE as the competitor. The natural processing and presentation of this epitope was demonstrated by recognition of an NY-ESO-1+ melanoma cell line by T cells with specificity for p134-148. The pentadecamer p134-148 was able to induce CD4+ responses in 4/38 cancer patients tested. However, no strict correlation was found between CD4+ T-cell responses against p134-148 reactivity and anti-NY-ESO-1 antibody titers in the serum of patients, suggesting that CD4+ and B-cell responses are regulated independently. In conclusion, p134-148 holds promise as a broadly applicable peptide vaccine for patients with NY-ESO-1-positive neoplasms.

HMB-45, S-100, NK1/C3, and MART-1 in metastatic melanoma

The diagnosis of melanoma metastatic to lymph node remains a difficult problem given its histological diversity. We examined the staining patterns of S-100, NK1/C3, HMB-45, and MART-1 (DC10) in melanoma metastases to lymph nodes. Immunohistochemical stains were performed on tissue sections of 126 formalin-fixed lymph nodes from 126 patients with an established diagnosis of metastatic melanoma. A total of 98% of cases (123 of 126) stained positive for S-100, 93% (117 of 125) stained positive for NK1/C3, 82% (103 of 126) stained positive for MART-1, and 76% (95 of 125) stained positive for HMB-45. The distribution and intensity of staining varied among these markers. A diffuse staining pattern, defined as >50% of tumor cells stained, was observed in 83% of MART-1-positive cases but in only 56% of S-100-positive cases, 48% of NK1/C3-positive cases, and 34% of HMB-45-positive cases. A maximally intense signal was almost always observed for MART-1 (83% of positive cases) but was rarely observed for NK1/C3 (20%). S-100 and HMB-45 showed maximally intense staining in 50% and 54% of cases, respectively. S-100 and NK1/C3 stained both histiocytes and melanocytes, whereas MART-1 and HMB-45 stained only melanocytes. Seventy-eight cases (63%) stained positive for all 4 markers, 17 cases (14%) stained for all markers except HMB-45, 13 cases (10%) stained for all markers except MART-1, 6 cases (5%) stained only with S-100 and NK1/C3, 4 cases (3%) stained only with S-100 and HMB-45, and 2 cases stained for all markers except S-100. One case each stained for the following: only S-100, only S-100 and HMB-45, and all markers except NK1/C3. One case exhibited absence of staining for any of these markers. We demonstrate that lymph node metastases of melanoma are heterogeneous with regard to tumor marker expression. S-100 and NK1/C3 were the most sensitive stains for detecting metastatic melanoma; however, they both also stain other nontumor cells in lymph nodes. MART-1 did not stain histiocytes and exhibited a more frequently intense and diffuse staining pattern than NK1/C3. HMB-45 was less sensitive and demonstrated less diffuse staining than MART-1.

Detection of micrometastases in sentinel lymph nodes from melanoma patients

The technique of sentinel lymph node (SLN) dissection is a reliable predictor of metastatic disease in the lymphatic basin draining the primary melanoma. Reverse transcription-polymerase chain reaction (RT-PCR) is emerging as a highly sensitive technique to detect micrometastases in SLNs, but its specificity has been questioned. A prospective SLN study in melanoma patients was undertaken to compare in detail immunopathological versus molecular detection methods. Sentinel lymphadenectomy was performed on 57 patients, with a total of 71 SLNs analysed. SLNs were cut in slices, which were alternatively subjected to parallel multimarker analysis by microscopy (haematoxylin and eosin and immunohistochemistry for HMB-45, S100, tyrosinase and Melan-A/MART-1) and RT-PCR (for tyrosinase and Melan-A/MART-1). Metastases were detected by both methods in 23% of the SLNs (28% of the patients). The combined use of Melan-A/MART-1 and tyrosinase amplification increased the sensitivity of PCR detection of microscopically proven micrometastases. Of the 55 immunopathologically negative SLNs, 25 were found to be positive on RT-PCR. Notably, eight of these SLNs contained naevi, all of which were positive for tyrosinase and/or Melan-A/MART-1, as detected at both mRNA and protein level. The remaining 41% of the SLNs were negative on both immunohistochemistry and RT-PCR. Analysis of a series of adjacent non-SLNs by RT-PCR confirmed the concept of orderly progression of metastasis. Clinical follow-up showed disease recurrence in 12% of the RT-PCR-positive immunopathology-negative SLNs, indicating that even an extensive immunohistochemical analysis may underestimate the presence of micrometastases. However, molecular analyses, albeit more sensitive, need to be further improved in order to attain acceptable specificity before they can be applied diagnostically.

Hyperpigmentation during interferon-alpha therapy for chronic hepatitis C virus infection

Many types of skin disorders concomitantly occur with hepatitis C virus infection. These skin lesions may be induced or worsened during antiviral therapy with interferon-alpha (IFN). To our knowledge, hyperpigmentation of the skin--and especially of the tongue--has not been reported so far. We describe two dark-skinned patients who developed hyperpigmented skin and tongue lesions during combination therapy with IFN and ribavirin. Immunohistochemical analysis of tongue biopsies confirmed the suspicion of melanin deposits in these areas of hyperpigmentation. We hypothesize that during interferon therapy, melanocytes may produce more melanin pigment in the presence of alpha-melanocyte stimulating hormone and sufficient amounts of tyrosine, leading to melanin deposits and clinical hyperpigmentation.

Detection of circulating melanoma cells by a two-marker polymerase chain reaction assay in relation to therapy

Malignant melanoma is one of the most rapidly increasing cancer types, and patients with metastatic disease have a very poor prognosis. Detection of metastatic melanoma cells in circulation may aid the clinician in assessing tumor progression, metastatic potential, and response to therapy. Tyrosinase is a key enzyme in melanin biosynthesis. The gene is actively expressed in melanocytes and melanoma cells. Melan A is a differentiation antigen that is expressed in melanocytes. The presence of these molecules in blood is considered a marker for circulating melanoma cells. In this study, we analyzed the usefulness of this marker combination in evaluating the response to therapy in the blood of 30 patients with malignant melanoma. Circulating cells were detected by a reverse-transcriptase-polymerase-chain reaction. The tyrosinase expression was observed in 9 (30%) patients and Melan A in 19 (63.3%) patients before therapy. Following treatment, the tyrosinase mRNA was detected in only one patient, while Melan A transcripts were still present in 14 patients. We suggest that this molecular assay can identify circulating melanoma cells that express melanoma-associated antigens and may provide an early indication of therapy effectiveness.

Surgical treatment of malignant melanoma

The surgical management of melanoma has evolved over the last 100 years. when early concepts of lymphatic permeation of the tumors and metastases led surgeons to perform radical operative procedures. Wide excision of primary melanoma is now performed with 1- to 2-cm radial margins, significantly reducing the need for complex plastic closures, skin grafts. and hospital admissions. Although elective lymph node dissection remains controversial as a therapeutic procedure, the development of SL has improved the staging of the regional lymph nodes and diminished the morbidity of lymph node dissection. The role of SL for routine care of melanoma patients remains unknown. Metastasectomy, which is the surgical resection of distant metastases with tumor-free surgical margins, has not been popular for AJCC stage IV patients with multiple metastases, because surgery is considered a local therapy and therefore of little value for management of disseminated disease. Nevertheless, the many reports of long-term survival after resection of distant melanoma metastases to diverse soft tissue and organ sites clearly indicate that this form of cytoreductive surgery can be extremely successful in carefully selected patients. Unlike chemotherapy, complete surgical metastasectomy can rapidly render a patient disease-free with only a short period of postoperative morbidity. Most patients fully recover from the surgical procedure within 6 weeks, returning to most or all activities. The ability to select patients for surgery is based on the development of more sophisticated imaging techniques, which allow better preoperative differentiation of patients with single versus multiple metastases and improve the surgeon's ability to identify and resect multiple metastatic sites. The overall data suggest that patients whose metastases can be completely resected will experience improved overall survival and occasional long-term cure regardless of the metastatic organ site and number of metastases. We believe that increased understanding of the biology of the primary and metastases, dramatic improvement in the accuracy of staging metastatic disease, and better techniques of surgical resection provide the best chance for long-term palliation or cure of melanoma. Cytoreductive surgery should be considered a form of immunotherapy. The long-term clinical benefit of this therapy depends on the patient's immune response to, the surgical reduction in tumor burden: an immune response that controls subclinical micrometastases should optimize postoperative survival.

Sentinel node biopsy: not only a staging tool?

The management of clinically negative regional lymph nodes in early-stage melanoma has been controversial for at least a century. While some surgeons offer elective lymph node dissection (ELND), others recommend treatment of the primary alone and only perform a therapeutic dissection (TLND) for cases of recurrence in the nodal basin. The rationale for ELND is based on the concept that metastases occur via the sequential passage of tumor from the primary site to the regional lymph nodes and then to more distant sites. If this theory is correct then early dissection of the regional lymph nodes will disrupt the metastatic cascade and prevent further spread of disease. On the other hand, advocates of the "wait and watch" approach suggest that metastases to the regional lymph node basin are only a marker of disease progression and that distant disease can occur in the absence of lymph node metastases. Four randomized prospective studies have examined the efficacy of ELND versus TLND. While all four studies have failed to demonstrate a survival advantage of ELND, there is some suggestion that patients with metastases in the regional basin may benefit from ELND. As an alternative approach to this controversy, Morton and associates at the John Wayne Cancer Institute devised the technique of intraoperative lymphatic mapping and sentinel lymphadenectomy (LM/SL). This minimally invasive operative procedure allows the surgeon to identify the first or sentinel lymph (SN) in the regional basin. The technique is predicated on accurate mapping of the cutaneous lymphatics by lymphoscintigraphy and the intraoperative use of a vital blue dye to lead the surgeon to the SN and allow the pathologists to identify metastases in the lymph nodes. Patients with tumor-positive dissections would undergo complete lymph node dissection (CLND), and for those without metastases the complications and costs associated with CLND could be avoided. The success of the procedure depends on the completion of a learning phase and on the cooperation of nuclear medicine physicians, surgeons, and pathologists. While this technique has become almost standard practice in the United States and around the world, we await the results of several important clinical trials to determine whether LM/SL will replace ELND or the wait and watch approach in the management of early-stage melanoma.

Comparison of five antibodies as markers in the diagnosis of melanoma in cytologic preparations

We determined the sensitivity and specificity of 3 novel antibodies (microphthalmia transcription factor [Mitf], Melan-A, and tyrosinase) as markers for melanoma in cytologic preparations and compared the results with those of commonly used markers (S-100 protein [S-100] and HMB-45). We stained 72 cell blocks from 40 patients with melanoma and 32 with nonmelanocytic malignant neoplasms with antibodies against S-100, HMB-45, Mitf, Melan-A, and tyrosinase. Histologic correlation was available in more than 95% of cases. Nuclear stainingfor Mitf and cytoplasmic stainingfor S-100, HMB-45, Melan-A, and tyrosinase in more than 10% of tumor cells was considered positive. All 3 novel markers demonstrated sensitivity superior to S-100 and HMB-45. HMB-45, Melan-A, and Mitf demonstrated specificities of 97%. S-100 protein and tyrosinase were less specific. Sensitivity and specificity for the combination Mitf+/Melan-A+ were 95% and 100%, respectively, whereas they were 80% and 100%, respectively, for S-100+/HMB-45+. Mitf Melan-A, and tyrosinase are sensitive markersfor epithelioid melanoma. Mitf and Melan-A seem more specific than S-100 and tyrosinase. An antibody panel consisting of Mitf and Melan-A is superior to a panel of S-100 and HMB-45 in the diagnosis of melanoma in cytologic specimens.

Cancer/testis antigens: an expanding family of targets for cancer immunotherapy

Cancer/testis (CT) antigens are a category of tumor antigens with normal expression restricted to male germ cells in the testis but not in adult somatic tissues. In some cases, CT antigens are also expressed in ovary and in trophoblast. In malignancy, this gene regulation is disrupted, resulting in CT antigen expression in a proportion of tumors of various types. Since their initial identification by T-cell epitope cloning, the list of CT antigens has been greatly expanded through serological expression cloning (SEREX) and differential mRNA expression analysis, and approximately 20 CT antigens or antigen families have been identified to date. Characteristics commonly shared by CT antigens, aside from the highly tissue-restricted expression profile, include existence as multigene families, frequent mapping to chromosome X, heterogeneous protein expression in cancer, likely correlation with tumor progression, induction of expression by hypomethylation and/or histone acetylation, and immunogenicity in cancer patients. Spontaneous humoral and cell-mediated immune responses have been demonstrated against several CT antigens, including NY-ESO-1, MAGE-A, and SSX antigens. Since CT antigens are immunogenic and highly restricted to tumors, their discovery has led directly to the development of antigen-specific cancer vaccines, and clinical trials with MAGE-A and NY-ESO-1 are in progress.

Autoantibodies in vitiligo patients are not directed to the melanocyte differentiation antigen MelanA/MART1

Recent studies have demonstrated the presence of circulating MelanA (MART1)-specific cytotoxic T lymphocytes in a significant number of vitiligo patients when compared to control subjects. High levels of the skin-homing receptor cutaneous lymphocyte-associated antigen were expressed on the T cells and their frequency correlated with the extent of depigmentation and disease activity in the vitiligo patients. The present study was designed to examine vitiligo patient sera for the presence of autoantibodies to MelanA. The incidence of autoantibodies to MelanA in patients with vitiligo (n = 51) and in healthy individuals (n = 20) was examined using a radiobinding assay with 35S]-labelled MelanA and using Western blot analysis with a glutathione S-transferase (GST)-MelanA fusion protein. Autoantibodies to MelanA could not be detected in any of the vitiligo patient sera or control sera analysed using either of these detection systems. It is therefore possible that MelanA only induces cellular rather than humoral autoreactivity in vitiligo.

The melanocytic protein Melan-A/MART-1 has a subcellular localization distinct from typical melanosomal proteins

To delineate the role of the melanocyte lineage-specific protein Melan-A/MART-1 in melanogenic functions, a set of biochemical and microscopical studies was performed. Biochemical analysis revealed that Melan-A/MART-1 is post-translationally acylated and undergoes a rapid turnover in a pigmented melanoma cell line. Immunofluorescence and immunoelectron microscopy analyses indicated that Melan-A/MART-1 is mainly located in the Golgi area and only partially colocalizes with melanosomal proteins. Quantitative immunoelectron microscopy showed that the highest proportion of the cellular content of Melan-A/MART-1 was found in small vesicles and tubules throughout the cell, whereas the concentration was maximal in the Golgi region, particularly the trans-Golgi network. Substantial labeling was also present on melanosomes, endosomes, ER, nuclear envelope, and plasma membrane. In early endosomes, Melan-A was enriched in areas of the limiting membrane covered by a bi-layered coat, a structural characteristic of melanosomal precursor compartments. Upon melanosome maturation, Melan-A concentration decreased and its predominant localization shifted from the limiting membrane to internal vesicle membranes. In conjunction with its acylation, the high expression levels of Melan-A in the trans-Golgi network, in dispersed vesicles, and on the limiting membrane of premelanosomes indicate that the protein may play a role during the early stage of melanosome biogenesis.

Magnetic bead RT-PCR: establishment of a new method for detecting circulating melanoma cells

This study was performed to detect circulating melanoma cells in peripheral blood using a novel method based on magnetic-activated cell separation (MACS) followed by a nested reverse transcriptase-polymerase chain reaction (RT-PCR) for tyrosinase and MART-1 mRNA. Samples to be tested were enriched for tumour cells either by isolating melanoma cells using two anti-melanoma antibodies (MART-1 and HMB-45) or by CD45 depletion of the non-melanoma cell fraction. The tumour cell-enriched fractions were subjected to mRNA isolation using oligo-deoxythymidylate (oligo-dT) magnetic beads followed by a nested RT-PCR. Sensitivity was assessed by spiking experiments and compared with a commonly used total RNA isolation system previously established in our department. Positive isolation of melanoma cells showed insufficient sensitivity, whereas negative isolation by depletion of leukocytes showed a detection limit of at least one melanoma cell per millilitre of whole blood. In further experiments, the depletion assay was applied to 25 peripheral blood samples of melanoma patients. The preliminary data obtained from the new method indicate a comparable detection rate to the established total RNA extraction method. However, not all the results were concordant. Therefore, future experiments need to be performed with a statistically greater number of patients.

CT7 (MAGE-C1) antigen expression in normal and neoplastic tissues

CT7 (MAGE-C1) is a member of the cancer testis (CT) antigen family. The present study describes the generation of CT7-33, a monoclonal antibody (MAb) to CT7, and the preliminary protein expression analysis of CT7 in normal tissues and in a limited number of neoplastic lesions. CT7-33 was effective in frozen as well as formalin-fixed, paraffin-embedded tissues, and immunohistochemistry/reverse transcriptase polymerase chain reaction (RT-PCR) co-typing demonstrated antibody specificity. CT7-33 immunoreactivity in normal adult tissues is restricted to testicular germ cells. In neoplastic lesions, CT7-33 immunostaining is confined to tumor cells, and the frequency of CT7 protein expression mostly parallels previous mRNA analyses. Whereas colorectal and renal cell carcinomas, as well as sarcomas, exhibit poor or no CT7-33 staining, carcinomas of the mammary gland and ovary, nonsmall cell lung carcinoma and metastatic melanomas exhibit a high incidence of CT7 protein expression. However, as seen in previous analyses of other CT antigens, the expression pattern is mostly heterogeneous, and tumors with more than 50% of tumor staining are only infrequently encountered. In summary, our study presents a new serologic reagent for the analysis of CT7 on a protein level and confirms what is known with regard to the expression pattern of other CT antigens in tumors: frequent heterogeneity of antigen expression.

Peptide vaccines for cancer

The revelation that immune cytolytic and helper T-cells recognize intracellularly degraded peptides processed via the proteosome apparatus, inserted into the endoplasmic reticulum and transported to the surface for association with major histocompatibility locus (MHC) molecules on specialized antigen-presenting cells has revolutionized the cancer vaccine field. Understanding the science of antigen processing and presentation has provided new reagents, delivery systems, and new investigative leads for the generation of immune responses against cancer. The cloning of tumor antigen genes has proceeded rapidly in melanoma, due to the ease with which melanoma-specific T-cells can be propagated in vitro, but breast, cervix, and lung cancer are not far behind. The cloning and identification of tumor antigens recognized by T-cells and data from initial clinical trials with peptides vaccines derived from those antigens are presented.

Use of immunocytochemical techniques in canine melanoma

The staining patterns of the monoclonal antibodies S-100 and Melan-A in canine melanoma were assessed based on cytological specimens of six canine melanomas (four benign, two malignant). In addition, eight regional lymph nodes of the two dogs with malignant melanomas were stained using these markers. For reference, all specimens were also evaluated immunohistochemically using S-100 and Melan-A. To assess the immunocytochemical specificity of both antibodies, various canine tumours and normal tissues were stained. The immunocytochemical staining results of the canine melanomas and the regional lymph nodes showed high conformity with the immunohistochemical reactivity patterns for S-100 and Melan-A. The specificity of Melan-A was higher compared with S-100. Melan-A, in particular, may be helpful for the cytological diagnosis of canine melanoma.

Mutation of melanosome protein RAB38 in chocolate mice

Mutations of genes needed for melanocyte function can result in oculocutaneous albinism. Examination of similarities in human gene expression patterns by using microarray analysis reveals that RAB38, a small GTP binding protein, demonstrates a similar expression profile to melanocytic genes. Comparative genomic analysis localizes human RAB38 to the mouse chocolate (cht) locus. A G146T mutation occurs in the conserved GTP binding domain of RAB38 in cht mice. Rab38(cht)/Rab38(cht) mice exhibit a brown coat similar in color to mice with a mutation in tyrosinase-related protein 1 (Tyrp1), a mouse model for oculocutaneous albinism. The targeting of TYRP1 protein to the melanosome is impaired in Rab38(cht)/Rab38(cht) melanocytes. These observations, and the fact that green fluorescent protein-tagged RAB38 colocalizes with end-stage melanosomes in wild-type melanocytes, suggest that RAB38 plays a role in the sorting of TYRP1. This study demonstrates the utility of expression profile analysis to identify mammalian disease genes.

Possible mechanisms of hypopigmentation in lichen sclerosus

Lichen sclerosus (LS) shares with vitiligo a milky-white appearance. By biopsy, pathognomonic dermal sclerosis readily distinguishes LS from vitiligo and other causes of leukoderma. To determine what the mechanism of hypopigmentation is in LS, we examined samples from LS cases for alterations in melanin content (Fontana-Masson stain) and melanocyte number (HMB-45 [PMEL-17/gp100], Mel-5 [TRP-1], Mart-1 [Melan A]) and compared these findings with those in controls of normal skin, acute scars, vitiligo, and lichen planus (LP; a common inflammatory cause of hyperpigmentation). The degree and extent of melanization found in LS overlapped with that in acute scars showing predominantly hypomelanized keratinocytes, with that in LP containing regions with numerous melanophages, and with that in vitiligo exhibiting focal regions of keratinocytes devoid of melanin pigment. By hematoxylin-eosin staining and immunocytochemistry for Mel-5 and Mart-1, LS had a lower mean count of melanocytes than acute scars, LP, and normal skin per 200 basal keratinocytes. In addition, a few LS cases had a significant loss of melanocytes comparable to that of vitiligo. Surprisingly, Mart-1 identified rare melanocytes in 67% of vitiligo cases and a significantly larger pool of melanocytes in LS and controls other than those labeled by Mel-5. Furthermore, LP and evolving lesions of LS contained the highest Mart-1 counts. HMB-45-immunoreactive melanocytes were found in the majority of acute scars and in LP and late-stage LS lesions at significantly lower levels than Mel-5- and Mart-1- labeled melanocytes, but they were not found in vitiligo or normal skin. We propose that several mechanisms may play a role in the production of leucoderma in LS: 1) decreased melanin production; 2) block in transfer of melanosomes to keratinocytes; and 3) melanocyte loss. The latter finding may be the pathogenic connection (lichenoid dermatitis of LS triggering an autoimmune reaction to melanocytes) that underlies the documented association of LS with vitiligo.

Role for microphthalmia transcription factor in the diagnosis of metastatic malignant melanoma

Microphthalmia transcription factor (Mitf), a protein critical for the embryonic development and postnatal viability of melanocytes, is a master lineage regulator and modulates extracellular signals. Recently, an anti-Mitf antibody, D5, was shown to be both a sensitive and a specific marker of epithelioid melanoma. Those data suggested that Mitf expression was specific for melanocytic differentiation because it was not detected in six different carcinoma types. To broaden the spectrum of melanomatous and nonmelanomatous tumors tested with this antibody, the authors investigated the sensitivity and specificity of the D5 anti-Mitf antibody in 36 metastatic melanomas and 102 nonmelanomatous tumors. Twenty-nine of 36 (81%) melanomas examined were reactive for D5. Of these, 29 of 32 (91%) epithelioid melanomas were reactive, whereas all 4 melanomas with spindle cell morphology were nonreactive. Six of 102 (5.8%) nonmelanomatous tumors (1 breast carcinoma, 1 malignant mixed mullerian tumor, 2 renal cell carcinomas, and 2 leiomyosarcomas) were reactive for D5. All melanomas were reactive for S-100 protein (a criteria for inclusion in the study), whereas 8 of 102 (7.8%) of nonmelanomatous tumors were reactive. Twenty-five of 36 melanomas (69%) were reactive for HMB-45, whereas no nonmelanomatous tumors were reactive. Twenty-one of 28 (75%) melanomas were reactive for Melan-A. Reactivity for Melan-A was detected in 5 of 102 (4.9%) nonmelanomatous tumors. As with D5, HMB-45 and Melan-A failed to detect all spindle-cell melanomas. Results of this study confirm that D5 is a sensitive marker for epithelioid melanomas; however, the authors found D5 neither quite as sensitive nor quite as specific as in previous studies. Nevertheless, the authors believe that positive staining for D5 when taken in clinical, histologic, and immunohistochemical context may be diagnostically useful. In particular, D5 is helpful in the evaluation of epithelioid neoplasms, but not spindle-cell tumors.

CpG are efficient adjuvants for specific CTL induction against tumor antigen-derived peptide

The identification of CTL-defined tumor-associated Ags has allowed the development of new strategies for cancer immunotherapy. To potentiate the CTL responses, peptide-based vaccines require the coadministration of adjuvants. Because oligodeoxynucleotides (ODN) containing CpG motifs are strong immunostimulators, we analyzed the ability of CpG ODN to act as adjuvant of the CTL response against tumor-derived synthetic peptide in the absence or presence of IFA. Mice transgenic for a chimeric MHC class I molecule were immunized with a peptide analog of MART-1/Melan-A(26-35) in the presence of CpG ODN alone or CpG ODN emulsified in IFA. The CTL response was monitored ex vivo by tetramer staining of lymphocytes. In blood, spleen, and lymph nodes, peptide mixed with CpG ODN alone was able to elicit a stronger systemic CTL response as compared with peptide emulsified in IFA. Moreover, CpG ODN in combination with IFA further enhanced the CTL response in terms of the frequency of tetramer+CD8+ T cells ex vivo. The CTL induced in vivo against peptide analog in the presence of CpG ODN are functional, as they were able to recognize and kill melanoma cells in vitro. Overall, these results indicate that CpG ODN by itself is a good candidate adjuvant of CTL response and can also enhance the effect of classical adjuvant.

Subcellular localization of the melanoma-associated protein Melan-AMART-1 influences the processing of its HLA-A2-restricted epitope

The peptide derived from the melanoma-associated protein Melan-A (Melan-A(26-35)/HLA-A2) is an attractive candidate for tumor immunotherapy but little is known about the intracellular processing of this antigen. Here we show that Melan-A is a single-pass membrane protein with an NH(2) terminus exposed to the lumen of the exocytic compartment. In transfected melanoma cells, Melan-A accumulates in the Golgi region. Inversion of the membrane topology leads to the retention of Melan-A in the endoplasmic reticulum. Most strikingly, melanoma cells expressing this form of Melan-A are more effectively recognized by specific CTL than those expressing either Melan-A in its native membrane orientation or Melan-A artificially localized in the cytosol. Our data are compatible with the notion that proteins retained in the endoplasmic reticulum are more efficiently degraded and produce more antigenic peptides.

CD34 expression in desmoplastic melanoma

BACKGROUND

Primary and metastatic malignant melanoma can simulate various soft tissue tumors, including dermatofibrosarcoma protuberans (DFSP). Expression of CD34, a marker characteristic of DFSP, as well as other spindle cell tumors, has not been previously documented in malignant melanoma.

METHODS

We present here an unusual case of metastatic malignant melanoma with a strong histologic resemblance to DFSP and also CD34 expression.

RESULTS

The patient, a 72-year-old man with a history of an invasive malignant melanoma of the skin of the right lower abdomen, presented with a right axillary mass. Histologic sections revealed intersecting fascicles of spindle cells with nuclear pleomorphism and numerous mitotic figures, diffusely infiltrating the adipose tissue in a pattern closely simulating that seen in DFSP. In other foci, epithelioid neoplastic cells with abundant cytoplasm, prominent nucleoli, nuclear pseudoinclusions, and focal cytoplasmic melanin pigment were seen. The neoplastic spindle cells were strongly labeled by two anti-CD34 monoclonal antibodies. Some of the spindle cells and the majority of the epithelioid neoplastic cells expressed S-100 protein and focally tyrosinase. The tumor cells were negative for HMB-45 and MART-1. Melanosomes were not identified by electron microscopy.

CONCLUSION

This case demonstrates the potential of melanoma to simulate DFSP closely, on both morphologic and immunohistochemical grounds, and confirms the utility of employing a broad panel of immunohistochemical reagents in problematic cases.

Immune responses to tumour antigens: implications for antigen specific immunotherapy of cancer

Tumour associated antigens recognised by cellular or humoral effectors of the immune system are potential targets for antigen specific cancer immunotherapy. Different categories of cancer antigens have been identified that induce cytotoxic T lymphocyte (CTL) responses in vitro and in vivo, namely: (1) "cancer testis" (CT) antigens, expressed in different tumours and normal testis, (2) melanocyte differentiation antigens, (3) point mutations of normal genes, (4) self antigens that are overexpressed in malignant tissues, and (5) viral antigens. Clinical studies with peptides and proteins derived from these antigens have been initiated to study the efficacy of inducing specific CTL responses in vivo. Immunological and clinical parameters for the assessment of antigen specific immune responses have been defined-delayed type hypersensitivity (DTH), CTL, autoimmmune, and tumour regression responses. Specific DTH and CTL responses and tumour regression have been observed after the intradermal administration of tumour associated peptides alone. Peptide specific immune reactions were enhanced after using granulocyte macrophage stimulating factor (GM-CSF) as a systemic adjuvant by increasing the frequency of dermal antigen presenting Langerhans cells. Complete tumour regression has been observed in the context of measurable peptide specific CTL. However, in single cases with disease progression after an initial tumour response, either a loss of single antigens targeted by CTL or of the presenting major histocompatibility complex (MHC) class I allele was detected, pointing towards immunisation induced immune escape. Cytokines to modulate antigen and MHC class I expression in vivo are being evaluated to prevent immunoselection. Recently, a new CT antigen, NY-ESO-1, has been identified on the basis of spontaneous antibody responses to tumour associated antigens. NY-ESO-1 appears to be one of the most immunogenic antigens known to date, with spontaneous immune responses observed in 50% of patients with NY-ESO-1 expressing cancers. Clinical studies have been initiated to evaluate the immunogenicity of different NY-ESO-1 constructs to induce both humoral and cellular immune responses in vivo.

Recurrent melanocytic nevus: a histologic and immunohistochemical evaluation

BACKGROUND

Recurrent melanocytic lesions may histologically resemble malignant melanoma.

METHODS

We evaluated the original nevi (ON) and recurrent nevi (RN) of 15 patients by routine histology and immunohistochemistry (IHC), examining expression of S-100 protein, gp100 (with HMB-45), MART-1, tyrosinase, and the Ki-67 proliferation marker.

RESULTS

Compared with ON, RN had a dermal scar, a significantly greater number of melanophages, and a greater extent of cellular atypia including prominent nucleoli and larger cell size. Architecturally, RN showed significantly less symmetry than ON; however, the percentage of junctional cohesive nests, the presence of suprabasal spread, and the degree of confluence were similar between ON and RN. Both ON and RN showed a decrease in expression of gp100 and tyrosinase with increasing depth ("maturation gradient") and low proliferative activity in both the junctional (4.6% for ON vs. 4.13% for RN) and the dermal components (0.93% for ON vs. 1.45% for RN).

CONCLUSIONS

RN exhibit a dermal scar, a greater number of melanophages, cytologic atypia, and asymmetry than ON, features that may raise concern about the possibility of malignant melanoma. However, the area with the irregular architectural pattern is restricted to the epidermis and dermis immediately above the scar. In addition, IHC helps to distinguish RN from malignant melanoma; specifically, RN demonstrate an immunohistochemical "maturation pattern" (with HMB-45 and anti-tyrosinase) and a low proliferative index (with Ki-67).

Detection of melanoma cells in sentinel lymph nodes, bone marrow and peripheral blood by a reverse transcription-polymerase chain reaction assay in patients with primary cutaneous melanoma: association with Breslow's tumour thickness

BACKGROUND

Tyrosinase reverse transcription-polymerase chain reaction (RT-PCR) has been shown to be highly sensitive in detecting tumour cells in melanoma patients.

OBJECTIVE

To assess whether the detection of minimal residual disease by RT-PCR is improved by concomitant analysis of sentinel lymph nodes (SLNs), bone marrow (BM) and peripheral blood (PB) in patients with primary melanoma.

METHODS

Thirty-five SLNs, 41 BM samples and 26 PB specimens from 26 patients with primary cutaneous melanoma (tumour thickness > or = 0.75 mm) were examined by nested RT-PCR for tyrosinase and Melan-A. SLNs and BM samples were also analysed by histopathology. RT-PCR findings were related to tumour thickness of the primary melanoma.

RESULTS

Overall, melanoma cells were detected by RT-PCR in 13 of 26 patients (50%). Seven patients had positive RT-PCR results in their SLNs (27%), including all patients (n = 4) with histologically positive SLNs, two patients had positive findings in their BM exclusively detected by RT-PCR (8%) and six patients in PB (23%). The presence of tumour cells detected by RT-PCR in SLNs was not related to the presence of melanoma cells in BM and/or PB. The incidence of RT-PCR-positive SLNs was significantly associated with greater tumour thickness (P = 0.004). Both patients with positive RT-PCR findings in their BM had a large tumour thickness (> or = 2 mm). No association between positive RT-PCR findings in PB and greater tumour thickness was observed.

CONCLUSIONS

RT-PCR-positive SLNs were strongly associated with greater tumour thickness, underlining the prognostic significance of SLN positivity. Similar to certain epithelial malignancies, molecular investigation of the BM might provide complementary prognostic information in the early stages of melanoma. In contrast, no association between positive RT-PCR results in PB and increasing tumour thickness was found, implying that RT-PCR findings in PB are of doubtful clinical relevance in primary melanoma.

A novel autocrine pathway of tumor escape from immune recognition: melanoma cell lines produce a soluble protein that diminishes expression of the gene encoding the melanocyte lineage melan-A/MART-1 antigen through down-modulation of its promoter

We have observed that malignant melanoma cells produce a soluble protein factor(s), which down-regulates melanocyte lineage Melan-A/MART-1 Ag expression by melanoma cells with concomitant loss of recognition by Melan-A/MART-1-specific T cells. This down-modulation of Melan-A/MART-1 expression, which we refer to as "Ag silencing," is mediated via its minimal promoter, whereas the promoter for the restricting Ag-presenting HLA-A2 molecule is not affected. Significantly, this Ag silencing is reversible, as removal of factor-containing supernatants from Melan-A/MART-1-expressing cells results in up-regulation of the promoter for the gene encoding this Ag, and renewed expression of the protein. We have evaluated over 20 known factors, none of which accounts for the Ag-silencing activity of the melanoma cell culture supernatants. The existence of this autocrine pathway provides an additional novel explanation for melanoma tumor progression in vivo in the presence of CTL specific for this melanocyte lineage Ag. These observations may have important implications for Melan-A/MART-1-specific CTL-mediated immunotherapy of melanoma tumors.

A potential immune escape mechanism by melanoma cells through the activation of chemokine-induced T cell death

The immune system attempts to prevent or limit tumor growth, yet efforts to induce responses to tumors yield minimal results, rendering tumors virtually invisible to the immune system [1]. Several mechanisms may account for this subversion, including the triggering of tolerance to tumor antigens [2, 3], TGF-alpha or IL-10 production, downregulation of MHC molecules, or upregulation of FasL expression [4, 5]. Melanoma cells may in some instances use FasL expression to protect themselves against tumor-infiltrating lymphocytes (TIL) [4, 5]. Here, we show another, chemokine-dependent mechanism by which melanoma tumor cells shield themselves from immune reactions. Melanoma-inducible CCL5 (RANTES) production by infiltrating CD8 cells activates an apoptotic pathway in TIL involving cytochrome c release into the cytosol and activation of caspase-9 and -3. This process, triggered by CCL5 binding to CCR5, is not mediated by TNFalpha, Fas, or caspase-8. The effect is not unique to CCL5, as other CCR5 ligands such as CCL3 (MIP-1alpha) and CCL4 (MIP-1beta) also trigger TIL cell death, nor is it limited to melanoma cells, as it also operates in activated primary T lymphocytes. The model assigns a role to the CXC chemokine CXCL12 (SDF-1alpha) in this process, as this melanoma cell-produced chemokine upregulates CCL5 production by TIL, initiating TIL cell death.

Immunoreactivity of A103, an antibody to Melan A, in canine steroid-producing tissues and their tumors

The monoclonal antibody A103 to the melanocytic differentiation antigen Melan A stains human steroid-producing cells and their tumors. A total of 200 formalin-fixed, paraffin-embedded canine normal tissues and hyperplastic and neoplastic lesions of the adrenal gland, testis, and ovary were immunohistochemically tested for Melan A with antibody A103. Leydig cell tumors (23/23, 100%), Sertoli cell tumors (14/15, 93%), and adrenocortical adenomas (12/13, 92%) were consistently positive. Adrenocortical carcinomas (23/35, 65%) and granulosa cell tumors (10/17, 59%) were less frequently positive. All pheochromocytomas, seminomas, and dysgerminomas were negative. The pattern of staining was cytoplasmic, but nuclear staining was also frequently seen in normal Leydig cells and their tumors. As in human tumors, immunohistochemistry for Melan A stains many canine steroid-producing tumors and can be used to distinguish these tumors from those of nonstereidogenic cells.

Expression of S100a, vimentin, NSE, and melan A/MART-1 in seven canine melanoma cells lines and twenty-nine retrospective cases of canine melanoma

We evaluated the expression of vimentin, S100a, and Melan A/MART-1 (melanoma antigen recognized by T cells 1) in seven cell lines established independently from dogs with canine melanoma. We also compared routine immunostaining of 29 clinical specimens from melanoma cases using vimentin, S100a, and neuron-specific enolase (NSE) with staining for Melan A/MART-1 as part of a diagnostic panel. All the cell lines were positive for expression of vimentin and S-100a. MelanA/MART-1 expression was seen consistently in only two of the seven cell lines. Staining for Melan A/MART-1 was most intense near areas of heavy melanin pigmentation. All except one of the clinical specimens were positive for vimentin. S 100a was expressed in the majority of both pigmented (15/20, 75%) and amelanotic (8/9, 88.8%) tumors. Seventeen of 29 (58.6%) tumors were positive for NSE. Melan A/MART-1 was expressed in 18/29 (62%) tumors, including 90% of pigmented tumors, but in no amelanotic tumors. Intensity of Melan A/MART-1 staining correlated positively with biologic behavior, with seven malignant tumors showing negative to weak staining and 10 benign tumors showing moderate to strong staining. Three malignant tumors showed moderate to intense staining for Melan A/ MART-1. Our results suggest that expression of Melan A/MART-1 may be unstable in cultured cell lines. Assessment of both S100a and Melan A/MART-1 expression is useful to confirm a diagnosis of canine melanoma, and Melan A/MART-1 may be especially informative regarding the biologic behavior of these tumors.